What pH level range indicates an alkaline substance?

An alkaline substance is characterized by a pH level that is greater than 7, with the range typically extending from 8 to 14. In the context of the provided choices, a pH level between 7.5 and 10 denotes a mildly alkaline substance, while a pH level in the range of 10 to 14 indicates a strongly alkaline or basic substance. Thus, the choice that indicates an alkaline substance correctly is the one that includes these higher pH values, particularly from 10 to 14.

Understanding pH levels is essential in cosmetology, as they can affect product performance and compatibility with hair and skin. Alkaline products can open hair cuticles, which is particularly relevant for processes like chemical straightening or lightening, making it crucial for cosmetology professionals to recognize and utilize the correct pH levels for various applications.